1. Field of the Invention
This invention relates to a process for the treatment of aqueous ethyl alcohol to remove impurities therefrom. More particularly, the invention relates to a process, using supercooling technology, for the treatment of aqueous ethyl alcohol, obtained by fermentation of a cereal, to prevent formation of certain impurities during the process of purification of aqueous ethyl alcohol, and to remove other impurities therefrom while maintain desirable organoleptic qualities in order to provide an improved, high alcoholic content beverage commonly referred to as vodka.
2. Reported Developments
Ethyl alcohol has been known and made since prehistoric times by fermentation of sugars using a yeast which changes the sugars into alcohol and carbon dioxide. The source of sugars is a cereal, such as potato and grain (wheat and corn and the like). The fermentation process is rather complex producing, in addition to ethyl alcohol, other substances including fusel oil, glycerin and various organic acids. The fermented liquid containing about 7 to 12 percent ethyl alcohol, the remaining portion being mostly water, is concentrated by distillation. The process of distillation not only concentrates the ethyl alcohol, but also removes a large portion of the unpleasant-tasting impurities. Repeated purification by distillation to remove most of the unwanted impurities also removes all of the flavoring elements which are necessary in potable liquors. Consequently, in the distillation of potable liquors, the process of removing unwanted impurities is only partially completed in order to save the desired flavoring elements. However, other methods are used to further remove unwanted impurities.
The removal of unwanted impurities is especially important in vodka since it is a pure beverage to which no flavors are added to mask the taste of impurities. It is a smooth, unaged, odorless and colorless mixture of about 40 to 50% alcohol and 50 to 60% water, with an extremely mild flavor.
To further purify vodka from impurities the original distillate is flowed through successive beds of activated charcoal. The charcoal traditionally used is made from hard wood, such as beech, maple, oak and hickory. U.S. Pat. No. 2,946,687 describes the use of a modified, partially activated hard-wood charcoal. While this process has been found to be effective to reduce the various impurities present in the alcohol-water mixture, the bottled vodka was found to have a haze of deposit impairing the appearance of the vodka. The source of this deposit was found to be the charcoal used in the process containing polyvalent calcium and manganese ions. U.S. Pat. No. 3,914,442 seeks to eliminate this problem by treating the charcoal treated alcohol with a highly-crosslinked nuclear sulfonic macroporous polystyrene cationic exchange resin and maintaining the pH of the vodka in the range of 7.2 to 9.
Other approaches to purification include blowing nitrogen gas through the alcohol-water solution. The nitrogen gas is said to become saturated with the vapors of ethyl alcohol and the volatile impurities are then drawn through an adsorbent which removes some of the impurities. U.S. Pat. No. 3,930,042 uses a carbon dioxide-containing gas counter--currently to a stream of alcohol in an amount sufficient to provide an alcohol-water mixture having a pH of between 4.0 to 5.5 to reduce impurities and to provide a stable vodka. U.S. Pat. No. 5,370,891 discloses a method for reducing impurities in vodka by using a low processing temperature of between 5.degree. C. to 20.degree. C. and flowing the vodka through three successive layers of activated charcoal.
While these and other similar approaches to reduce impurities were at least partially successful in producing a popular beverage generally known as Russian vodka, the need still exists to produce vodka more economically which has less impurities, possess excellent organoleptic properties and increased shelf-life.